Herbicides comprise a category of agricultural chemicals intended to control or destroy weeds that interfere with the growth and development of cash or ornamental crops, or of vegetation that otherwise require removal for fire safety, aesthetic or other reason. Control of such undesirable vegetation is desirable in farms and orchards; rights-of-way, roadsides, paths and industrial areas; for incidental control of weeds in gardens, parks, and playgrounds (such as school playgrounds); and for other applications typically requiring herbicidal action.
Herbicides can be categorized as having “pre-emergence” action that either prevents germination of weed seeds or kills the emergence seedlings, or “post-emergence” action that kills the unwanted plant as it grows and develops following germination. Post-emergence herbicides that are absorbed into plant tissue and translocate to one degree or another throughout the plant for an herbicidal effect, can be classified as “systemic” herbicides. Systemic herbicides can induce systemic phytotoxicity in a plant, killing or severely damage the entire plant including its roots such that regrowth is either prevented or significantly reduced. Systemic herbicides can be classified as “non-selective” if formulated to kill a wide variety of targeted plant species, or as “selective” if formulated to kill only specifically targeted weeds. Some post-emergence herbicides can also be classified as “topical” herbicides, and can result in topical phytotoxicity, for example as defoliants, or dessicating or killing portions of a plant, for example shoots or growths off of an established plant, such as “suckers” that grow off of an established grape vine.
There currently exists a category of non-systemic post-emergence “burn-down” herbicide that, as a result of the chemical destruction of protective surface tissues kills by severe desiccation and “sun burn”. “Commercial and non-organically certified examples of burndown herbicides include glyphosate (e.g., “Roundup” at reduced rates, Monsanto), paraquat dichloride (“Gramazone”, Syngenta), and 3,6-dichloro-2-methoxybenzoic acid (“Vanquish”, Nufarm). At higher rates Roundup is also an effective “systemic” herbicide that kills both the foliage and roots of the plant and thus can prevent regrowth. Burndown herbicides do not typically kill below-ground tissues and regrowth can occur.
The active ingredients of a variety of herbicides certified as “organic” by the Organic Materials Review Institute (“OMRI”) include household vinegar (acetic acid 5-7%), acetic acid (e.g., 30% acetic acid, glacial acetic acid), “citrus oil”, lemon oil, clove oil, cinnamon oil, and various combinations of these and similar substances. The active ingredients of OMRI certified proprietary herbicides can include one or a combination of fatty acids, examples of which are caprylic and capric acids (“Suppress”, Westbridge Agricultural Products) and pelargonic acid (“Scythe”, Dow Agro Sciences). Ammonium nonanoate salt is the active ingredient of the OMRI burndown herbicide “AXXE” (BioSafe Systems). To the best of Applicant's knowledge, all herbicides currently certified by OMRI are “burndown” herbicides, and are represented as non-systemic in their action. Roots or below-ground meristems (typical of grasses) are left unaffected, re-grow, and can require additional treatments for control.